Recently, the number of drive pins for an organic EL display device tends to be increased according to a demand of further higher resolution. For this reason, the drive frequency thereof is raised and the power consumption tends to be increased.
Since number of pins for a QVGA full color in an organic EL display device now under development reaches 360 wherein 120 pins respectively for R, G and B, three drivers therefor are now necessitated. Such an increase of the terminal pin number increases power consumption in a column driver IC. Therefore, reduction of the power consumption is demanded.
Now a technology in which organic EL elements are current driven with low power consumption by making use of a DC/DC converter is known (patent document 1).
Patent document 1: JP-2001-143867A
On the other hand, noting difference in light emission efficiency for R, G and B, the present applicant invented the following technology and has filed as Japanese patent application No. 2003-166067 titled “Organic El drive circuit and organic EL display device using the same”.
In the invention, through respective provision of a first power source line having a high voltage and a second power source line having a lower voltage than that of the first power source line depending on the light emission efficiency of organic EL elements for R, G and B, current source voltages for driving the organic EL elements for R, G and B are made different. Then, the organic EL elements having higher light emission efficiency are assigned to the second power source line of which electric power is supplied from the first power source line for the organic El elements having lower light emission efficiency via a switching regulator and with the switching regulator the voltage of the second power source line is stabilized at a predetermined voltage.